This invention is concerned with handling multi-component compositions, e.g. comprising two or more components which, when mixed, form an adhesive composition. (Although the following disclosure describes only a system for the supply of two components, it will be appreciated that the system could readily be adapted to cater for three or more components, should the need arise, and the invention is to be understood as relating to systems for handling two or more components.)
Two-component adhesive compositions are well known, usually comprising a first component which is referred to as the "hardener" and a second component which is usually referred to as the "adhesive". Two-part adhesive compositions of this kind are for example polyurethane compositions, neoprene compositions and indeed rubber solutions.
In the case of such two-component compositions it is desirable to maintain the two components separate until they are required for use, since once they are mixed the composition tends to "cure" relatively rapidly, so that there is only a relatively short time available between mixing and application. Moreover, where the amount of composition applied in any one application is relatively small, it is not appropriate to pre-mix even a relatively small batch in preparation for a series of such application steps.
In the case of certain of these compositions, in particular the hardener must be handled with great care because of risks which could otherwise arise of injury to the operator or other people in the vicinity of its use. For example, it is undesirable to supply the hardener in a pressurised system unless adequate safeguards are taken against the risk of leakage, which could lead to the hardener being sprayed; such precautions, of course, are costly. Moreover, at least certain of the hardeners are susceptible of changing their characteristics in the presence of moisture, so that using a pressurised system which involves the use of air under pressure coming into contact with the hardener will require that air to be "dry air"; again this is a costly provision. Moreover, certain of the hardeners are known to become liable to cause an explosion when pressurised by the application of air under pressure.
Also in handling components which make up e.g. polyurethane or neoprene compositions, attention has to be given also to the dangers involved, especially in the case of the hardener, which may be toxic. Thus it is desirable that a closed, leak-proof, system be utilised for the supply of such components. In this regard, for example, it may be considered that a piston-an-cylinder arrangement, which relies upon seals (piston rings) to prevent leakage, would not be adequate, even though from the point of view of metering the provision of such arrangements for each component may be considered otherwise attractive.